A timer is a device that counts down a specific amount of time, alerting users when the time is up. Timers are commonly used in cooking, sports, and various activities where time management is essential. They can be mechanical or digital, with many modern timers found in smartphones and kitchen appliances. Timers can also be used for counting up, measuring elapsed time for activities like workouts or experiments. Some timers have additional features, such as multiple countdowns or alarms, making them versatile tools for both personal and professional use.